The present disclosure relates to a brake pad for a disc brake of a vehicle.
For vehicles, particularly rail vehicles, which reach high speeds, brake pads are used whose friction elements consist of a hard material.
In order to achieve a satisfactory contact pattern, that is, a uniform surface pressure of the friction elements on the friction surface of the brake disc, various constructive solutions are known.
Thus, cup springs are used, for example, which are supported on the back of the carrier plate and by which the connected friction elements are elastically disposed on the carrier plate. In another construction, the friction elements are elastically guided on spiral springs, while, according to another suggestion, the friction elements are connected with deformable intermediate metal sheets.
A so-called isobar brake pad is known from European Patent Document EP 0 784 761 B1 (corresponding to U.S. Pat. No. 5,934,418) as well as German Patent Document DE 197 09 962 C1. In this case, the friction elements have spherical-segment-shaped areas on their side facing the carrier plate, which spherical-segment-shaped areas rest in ball sockets of the carrier plate adapted thereto. In the last-mentioned prior art, the friction elements, which otherwise have a hexagonal base, are held by tension springs which are supported on the back of the carrier plate.
In the case of the known brake pads, problems arise because of the relatively high-expenditure and cost-intensive production and a frictional behavior of the friction elements respectively. The frictional behavior is not quite sufficient because of the poor contact pattern despite the constructive measures carried out.
It is therefore an object of the present invention to further develop a brake pad of the above-mentioned type such that the frictional behavior of the friction elements is optimized and a more cost-effective production is permitted.
The integrated elasticity of shape of the carrier plate of the present disclosure improves the contact pattern as a whole and avoids, in particular, so-called “hot spots”, an overstressing of areas as a result of non-uniform heating.
According to an advantageous further development of the present first type of brake pad, in which, corresponding to German Patent Document 197 09 962 C1, the friction elements are each fastened by tension springs on the carrier plate, a rigid connection subject to the risk of fracture between the two components is prevented. The risk of fracture would exist, for example, in the case of a riveted or welded connection, so that this connection represents a considerable improvement of the operational reliability.
This also applies to a second type of brake pad, in which, in addition to the rear-side tension spring, by means of which the respective friction element is fastened to the carrier plate, another spring element is arranged between the friction element and the carrier plate. The spring element rests in a receiving device of the carrier plate, which is built into the side facing the friction element.
The dimensions of the receiving device are such that the spring element with a round base plan rests in it in an axially as well radially secured manner.
The tension spring is prestressed such that the friction element is constantly clamped in, thus also in the relaxed position of the spring element.
In comparison to the partial deformability of the carrier plate of the first type of brake pad, the spring elements consisting of spring steel have a greater elasticity. When the spring elements are used, the carrier plate can be produced from a low-cost casting material or from low-strength steel sheet, whereby noticeable cost advantages are achieved.
Another contributing fact is that, in principle, only a few different components are present, specifically the carrier plate, the friction elements, the tensions springs and, in the case of the second type of brake pad, the spring elements. Furthermore, the simple construction permits an easy exchangeability of the friction elements because of wear, so that repair-caused interruptions of the operation can be kept extremely brief.
Such a modular construction of this brake pad also has the result that the friction element and spring components can be used unchanged, so that existing parts can be used without any problem. Thus, only the carrier plate has to be modified corresponding to the disclosure.
In principle, the carrier plate according to the present first type of brake pad can be produced by precision casting, which is particularly cost-effective. In addition to the construction as a cast steel or aluminum part, the construction as a deep-drawn steel sheet part is conceivable.
According to another concept of the disclosure, radial slots are made in the area of the ball sockets of the carrier plate. The radial slots provide the ball sockets with a certain elasticity perpendicular to the friction surface. Instead of the slots, which extend continuously from the ball socket to the rear side of the carrier plate, grooves can also be provided by means of which the desired elasticity can also be achieved.
In addition to the above-mentioned radial arrangement of the slots, other arrangements are also conceivable. The elasticity in each case is achieved by a partial weakening of the material of the carrier plate.
This is also the case in an embodiment in which the ball socket is constructed in the sense of a cup spring, viewed over the radius, the thickness of the material being constant or changed.
Instead of the above-mentioned locally limited elasticity of the carrier plate, a locally unlimited elasticity can be provided which occurs outside the ball socket.
For this purpose, it is conceivable to dimension the carrier plate to be thinner and to provide elevations in the form of knobs or the like in the overlapping area of the friction elements. The knobs or the like are used as a support for the friction elements.
As a result of a uniform course of the thickness of the carrier plate or a course which is changed in a defined manner, a more or less elastic deformation can be established in the contact area of the friction elements.
Slots or grooves in the carrier plate outside the ball sockets which are arranged in a defined manner permit a certain elasticity in the supporting areas for the friction elements.
A further development of the second type of brake pad of each spring element is constructed as a form spring and has a concentrically arranged ball socket in which the spherical-segment-shaped area of the element rests. As a result of this form closure, a radial fixing of the friction element is also achieved. This also exists when the corresponding area of the friction element is not spherical-segment-shaped but conical and the form spring is adapted thereto in its receiving area.
The form spring simultaneously has a stop by which its spring deflection is limited.
Instead of the form spring, a cup spring can be used as a spring element. Since a commercially available standard part can be used here, this variant represents a particularly cost-effective solution.
Here, a positioning of the friction element is achieved by the center bore of the cup spring, in which either the spherical area of the friction element or a cylindrical or conical attachment rests.
As a result of a local plasticizing because of occurring contact pressure forces, the edge area of the center bore can be pressed so far into the spherical or conical area of the friction element that a form closure, which is exact with respect to the measurements, and a play free fit is achieved virtually without machining.
Expediently, the diameter of the receiving device of the carrier plate in which the cup spring rests is smaller than the assigned dimension of the friction element. The edge area of the carrier plate adjacent to the receiving device forms a stop, on which the friction element rests in the end position. Thus, the carrier plate bounds the spring travel of the cup spring.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.